Method for producing peroxydicarbonates and their use in the radical polymerization of monomers

ABSTRACT

A process for producing peroxydicarbonates comprising first reacting at least one inorganic peroxide with at least one alkali metal hydroxide to form at least one alkali metal peroxide. The at least one alkali metal peroxide is added to a mixture of at least one haloformate, at least one dispersant and water. The mixture is homogenized during the entire reaction to form a peroxydicarbonate. The peroxydicarbonate is dispersed as small droplets of from 1 to 10 microns in size in the aqueous mixture. The entire mixture is added to a polymerization reactor containing an ethylenically unsaturated monomer. The peroxydicarbonate functions as the free radical initiator to polymerize the monomer. The peroxydicarbonate is substantially free of organic solvents and plasticizers. The resulting polymers are of high quality.

BACKGROUND OF THE INVENTION

[0001] Peroxydicarbonates are important for use as free radicalproducing initiators in the polymerization field, and particularly inthe polymerization of ethylenically unsaturated monomers, such as vinylchloride. Peroxydicarbonates are typically made in large batches andsold in pure form either as neat or diluted products. Polymer producersmust store large quantities of the peroxydicarbonates for use in theirpolymerization processes. Precautions must be taken with the storage andhandling of these materials as they are unstable and are sensitive toboth thermal and impact shock and can detonate under certain conditions.Complying with all of the safety requirements of handling thesematerials results in the peroxydicarbonates being very expensive toemploy in the manufacture of polymers.

[0002] Various solutions to this problem have been proposed in the past.U.S. Pat. No. 4,359,427 proposes a process to continuously produce andpurify the peroxydicarbonates on the polymerization site and to storethem in a diluted phase until used. Another approach that has beensuggested is to produce the peroxydicarbonates in the largepolymerization vessel before adding the polymerizable monomer. Makingthe peroxydicarbonates in a large vessel has resulted in qualityproblems for the polymer being produced for several reasons. One suchreason is that there is not adequate mixing of the small amount ofreactants in a large reactor vessel. Without adequate mixing thereaction to form the peroxydicarbonates is inefficient and the yield ofperoxydicarbonate produced varies, thus making the polymerizationreaction using the peroxydicarbonates initiator(s) vary in reactiontime. To make greater volumes, diluents are often used, such as solventsand water. With these diluents there is poor conversion of the reactantsresulting in large amounts of undesirable by-products which are formedand which remain in the large reactor to contaminate the polymer that isultimately produced in the reactor. Solvent dilution results in solventbeing present which must be recovered and contaminates the recoverysystem for recovering unreacted monomer. Also, by making theperoxydicarbonate in the large polymerization vessel, productivity islowered because the polymerization vessel is occupied with theperoxydicarbonate synthesis process before each batch of polymer can beproduced.

[0003] Great Britain Patent 1,484,675 proposes to solve these problemsby producing the peroxydicarbonates outside of the polymerization vesselin the presence of a solvent to obtain adequate mixing of the reactants.This method is undesirable because the solvent must be removed or elseit becomes a contaminant in the polymerization process and contaminatesthe polymerization process monomer recovery system.

[0004] WO 97/27229 patent application proposes to solve the problem bymaking the peroxydicarbonates outside of the polymerization reactor in atwo-step process and adding a water insoluble liquid dialkylalkanedicarboxylate. The dialkyl alkane dicarboxylate is a plasticizerfor the resulting polymer and is undesirable in rigid applications ofthe polymer. Also, the two-step process is cumbersome and requiresexcess equipment.

[0005] U.S. Pat. No. 4,359,427, Great Britain patent 1,484,675 and WO97/27229 all teach that the peroxydicarbonates can be produced byreacting a chloroformate with an alkali metal peroxide.

SUMMARY OF THE INVENTION

[0006] It has been unexpectedly found that a peroxydicarbonate initiatorcan be produced at a polymerization site outside of the polymerizationvessel which when used in polymerizing ethylenically unsaturatedmonomers gives high quality polymers. The process for making theperoxydicarbonate of this invention involves first mixing an alkalimetal hydroxide with a peroxide to form an alkali metal peroxide. Thealkali metal peroxide is added to a mixture of haloformate, dispersantand water to form the desired peroxydicarbonate. The reaction mixture ishomogenized during the reaction to give small droplets ofperoxydicarbonates. The resulting peroxydicarbonates do not need to bediluted with solvents or plasticizer nor do they need to be purified.The resulting peroxydicarbonates are produced immediately prior to apolymerization reaction and charged to the polymerization vessel and thepolymerization reaction is conducted to give a high quality polymer fromthe ethylenically unsaturated monomer.

DETAILED DESCRIPTION

[0007] Peroxydicarbonates produced by this invention have the generalformula:

[0008] R and R¹ are different or identical organic radicals having from2 to 16 carbon atoms, preferably 2 to 10 carbon atoms, and morepreferably from 2 to 6 carbon atoms. The most preferredperoxydicarbonates have R and R¹ as identical radicals. Specificexamples of R and R¹ are alkyl radicals such as ethyl, n-propyl,isopropyl, n-butyl, isobutyl, secondary butyl, amyl, hexyl or2-ethylhexyl; alkenyl, aryl, alkylaryl, arylalkyl or cycloakyl radicals,or radicals derived from heterocyclic compounds and, particularlyradicals such as benzyl, cyclohexyl, cinnamyl, tetrahydrofuryl, and alsotheir substituted derivatives. The most preferred peroxydicarbonates arediethyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di-isopropylperoxydicarbonate, di-n-butyl peroxydicarbonate, di(secondary butyl)peroxydicarbonate and di(2-ethyl hexyl) peroxydicarbonate.

[0009] The haloformates used to produce the peroxydicarbonates have thegeneral formula:

[0010] wherein R² is an organic radical containing from 2 to 16 carbonatoms and R³ is a halogen atom. R² is the same organic radical asdescribed above for R and R¹. R³ is a halogen, such as chlorine,fluorine, iodine or bromine. Preferably R³ is chlorine. One or more thanone haloformate may be used to produce the peroxydicarbonate.

[0011] At least one dispersant is used in the synthesis of theperoxydicarbonate such as hydrolyzed polyvinyl acetates, alkyl andhydroxyalkyl cellulose ethers such as methyl cellulose, hydroxypropylmethyl cellulose, gelatin, polyvinylpyrrolidone, polyoxyethlyenesorbitan monolaurate, polyacrylic acid and like compounds. Thedispersant is preferably selected to be similar to the dispersant usedin the polymerization of the ethylenically unsaturated monomer. Forpolymerizing vinyl chloride monomer, the preferred dispersant inhydrolyzed polyvinyl acetate having a hydrolysis in the range of about70% to about 90%. The dispersant is preferably added as a watersolution. The level of dispersant used should be sufficient to form awater emulsion of the haloformate. This level is normally from about0.05 to 0.2 gram of dispersant per gram of haloformate, preferably fromabout 0.075 to about 0.1 gram of dispersant per gram of haloformate. Thedispersant is added as a water solution. The solution has from about 1%to about 10% by weight of dispersant in water, preferably from about 3%to about 8% by weight of dispersant in water. Once the reaction to formthe peroxydicarbonate is complete, additional dispersant may be added tostabilize the emulsion. Stabilizing the emulsion is particularlyimportant if the peroxydicarbonate is not used shortly after being made.

[0012] Water is also used in the synthesis of peroxydicarbonates of thisinvention. The water is required to disperse the dispersant and otherreaction ingredients. Water also assists in removal of the heatresulting from the exothermic reaction. Preferably the water used isdemineralized water. The amount of water used is not critical exceptthat the amount necessary to disperse the dispersant and dissolve thealkali metal hydroxide and peroxide must be used. The alkali metalhydroxide and peroxide are used as aqueous solutions and thus provide aportion of the required water. Preferably a minimum amount of water isused to get the required cooling. An excess of water, over that requiredto disperse the reactants and provide cooling, should be avoided duringthe reaction so as to give more intimate contact of the reactants. Oncethe reaction is complete, additional water may be added. Normally theamount of water used for the reaction is from about 5 grams to about 20grams of water per gram of haloformate, preferably from about 7 grams toabout 12 grams of water per gram of haloformate. A majority of the wateris added as a result of adding the ingredients as a water solution.

[0013] At least one alkali metal peroxide is used in the synthesis ofthe peroxydicarbonates of this invention. The preferred alkali metalperoxide is sodium peroxide. The alkali peroxide is formed from reactingan inorganic peroxide such as hydrogen peroxide with an alkali metalhydroxide, such as sodium hydroxide, potassium hydroxide, ammoniahydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide andalkali metal phosphates. The preferred sodium peroxide is formed byreacting sodium hydroxide with hydrogen peroxide. Two moles of alkalimetal hydroxide are used for every one mole of inorganic peroxide. Anexcess of either reactant can be used, but would not be preferred.

[0014] One method to produce the peroxydicarbonates of this invention,is to use two reaction vessels. The reaction vessels may be of any shapeand material, but the shape and material of construction should beconducive to being cooled. Metal vessels such as stainless steel pots orpipes are satisfactory. In one vessel, the alkali metal peroxide isproduced by mixing the alkali metal hydroxide with inorganic peroxide.The mixture of the alkali metal hydroxide and inorganic peroxide arethoroughly mixed by conventional mechanical agitation to form the alkalimetal peroxide. In making the preferred alkali metal peroxide, sodiumhydroxide is mixed with hydrogen peroxide to produce sodium peroxide.The preferred sodium hydroxide used is a water solution of sodiumhydroxide. The concentration of sodium hydroxide is not critical but thepreferred concentration is a 5% to 35 weight % percent solution ofsodium hydroxide in water, with the preferred concentration being at 5%to 15 weight % solution of sodium hydroxide. The hydrogen peroxide usedis more preferably a 5% to 10 weight % solution of hydrogen peroxide inwater.

[0015] The mixture used to make the alkali metal peroxide is two molesof alkali metal hydroxide with one mole of inorganic peroxide. Thereversible reaction can be shown for the preferred ingredients as:

2NaOH+H₂O₂

Na₂O₂+2H₂O

[0016] The temperature of the reaction needs to be below thedecomposition temperature of the alkali metal peroxide. Also, themixture should be cooled so as not to add heat when later used to makethe peroxydicarbonate. For the preferred alkali metal peroxide, thealkali metal peroxide is cooled to less than 28° C. and more preferablyto a temperature of from 0° C. to 10° C.

[0017] In the second vessel equipped with a homogenizer apparatus andcooling means, the haloformate, dispersant and water are added. Themixture of haloformate, dispersant and water is cooled and homogenizedwhile adding the alkali metal peroxide from the first vessel. It ispreferred to start the homogenization before the alkali metal peroxideis added and continue until all of the alkali metal peroxide has beenadded. The temperature of the mixture of the second vessel should bemaintained below the decomposition temperature of the peroxydicarbonateto be formed. For the preferred reactants, the temperature should bemaintained below 40° C., preferably below 22° C. and more preferablyfrom 0° C. to 10° C. Because water is present, the mixture should not becooled low enough to freeze the water, although the freezing temperatureof the water in the mixture is lower than 0° C. because of the presenceof by-products (salts). If the temperature is above the decompositiontemperature of the peroxydicarbonate formed, efficiency is lowered asthe peroxydicarbonate will decompose. Decomposition can be observed byfoaming caused by the liberation of carbon dioxide when theperoxydicarbonate decomposes. The alkali metal peroxide can be added tothe second vessel at a rate which is determined by the ability to coolthe second vessel, such as not to exceed the decomposition temperatureof the peroxydicarbonate formed. The reaction of the alkali metalperoxide and haloformate are almost instantaneous, but are extremelyexothermic. Because of the highly exothermic reaction, it is preferredto meter the alkali metal peroxide from the first vessel to the secondvessel containing the haloformate over a period of from about 2 to about20 minutes. The rate of addition of the alkali metal peroxide isdependant only on the ability to cool the reaction, such as to maintainthe reaction temperature below the decomposition temperature of theperoxydicarbonate being formed.

[0018] The haloformate, dispersant and water mixture of the secondvessel could be added to the first vessel containing the alkali metalperoxide but this method is less efficient in that yields ofperoxydicarbonate are lower.

[0019] The levels of reactants used in the second vessel are one mole ofalkali metal peroxide for every two moles of haloformate. The reactioncan be shown for the preferred reactants as:

[0020] wherein R² is an ethyl group in the most preferred embodiment ofthis invention.

[0021] Homogenization of the ingredients in the second vessel is veryimportant and a critical feature of this invention as it providesintimate contact between the reactants thus resulting in the need to useless reactants. By using less reactants, the need to dilute the reactionwith a solvent or a plasticizer is unnecessary thus resulting in lessby-products which are harmful in the polymerization process of theethylenically unsaturated monomer. The homogenization also givesperoxydicarbonate droplets having a diameter less than 10 microns,preferably less than 5 microns and more preferably from 1 to 4 microns.The small droplet size of peroxydicarbonate is advantageous in producingpolymers having low levels of gels.

[0022] The type of homogenizer apparatus found to be suitable for largerscale reactions in this invention is an Arde Barinko homogenizer. Thistype of homogenizer apparatus has a shaft extending into the reactantsof the second vessel. The shaft end has narrow slits (teeth) in thefixed stator with a rotating disc having teeth offset from the teeth inthe stator, such that the reactants are drawn into and repeatedly cycledthrough the narrow slits in the stator. For small scale laboratoryreactions, a homogenizer of the tissue tearer type such as FisherSchientic #15-338-51 can be employed.

[0023] An alternate method to make the peroxydicarbonates of thisinvention for use in a polymerization process to produce polymers fromethylenically unsaturated monomers, is to use an in line homogenizer.When using an in-line homogenizer, the haloformate, dispersant and waterare injected into a line, such as a pipe. The pipe is connected to ahomogenizer. The alkali metal peroxide may be metered into the line justprior to the homogenizer, or preferably in a recirculating line betweenhomogenization passes. This method provides for the homogenization ofthe haloformate before adding the alkali metal peroxide andhomogenization after combining all ingredients. Examples of suitablein-line homogenizers are the those sold under the name Manton Gaulinhomogenizer. The ingredients to be homogenized can be passed through thehomogenizer multiple times until the desired homogenization is obtained.For making the peroxydicarbonates of this invention, sufficienthomogenization should be performed to give a droplet size of theperoxydicarbonate of from about 1 to 10 microns, preferably from about 1to about 4 microns. The line where the peroxydicarbonates are formed isconnected to the polymerization reactor and pumped into the reactor atthe desired time. The line is flushed clean with water after theperoxydicarbonate is charged to the polymerization reactor.

[0024] If it is desired to produce more than one peroxydicarbonate foruse in a polymerization, then the reaction to form the firstperoxydicarbonate should be completed before adding the secondhaloformate and the corresponding alkali metal peroxide. If twodifferent haloformates are mixed and alkali metal peroxide is added,then three different types of peroxydicarbonates will be formed. Twotypes will be symmetrical with the same end groups on each end, whilethe third type will have a different end group on each side. Althoughthis type of peroxydicarbonate mixture would function as an initiatorfor polymerization, it is not the most desirable mixture. The specificamounts of each of the three different types of peroxydicarbonatesformed is not believed to be well controlled and can vary from batch tobatch. For this reason, it is preferred to complete the reaction of thefirst peroxydicarbonate before beginning the reaction to form the secondperoxydicarbonate. Should a third or subsequent peroxydicarbonate bedesired, then the reaction to complete the second peroxydicarbonateshould be completed before adding the haloformate to produce the thirdperoxydicarbonate and so forth for each additional desiredperoxydicarbonate.

[0025] The reaction in the second vessel to produce theperoxydicarbonate preferably should be completed just prior to when itis needed in the polymerization cycle. Should there be an unplanneddelay in using the peroxydicarbonate, the aqueous mixture in the secondvessel containing the peroxydicarbonate should be agitated. It ispreferred that the second vessel contain an agitation system, as well asthe homogenization system. The agitation is necessary because thepreferred peroxydicarbonate is heavier than the aqueous salt mixture itis suspended in and will settle to the bottom over time if not agitated.The stability of the other peroxydicarbonates, other than di-ethylperoxydicarbonate, are greater in that they are less dense, butagitation is still preferred should the use of the peroxydicarbonate bedelayed. A simple agitation is preferred rather than continuing to runthe homogenizer, since the homogenizer will add heat to the aqueousdispersion of the peroxydicarbonate, which is undesirable. Any type ofsystem for the agitation is acceptable, such as a shaft with blades or amethod to bubble inert gas into the vessel, as long as theperoxydicarbonate is not allowed to settle on the bottom of the vessel.

[0026] Various peroxydicarbonates can be made by the process of thisinvention. The nature, or structure of the initiator produced willdepend upon the particular haloformate employed in the reaction. Theperoxydicarbonates can be used in the suspension polymerization ofethylenically unsaturated monomers. As examples of the ethylenicallyunsaturated monomers, there may be named the vinyl halides, such asvinyl chloride, vinyl bromide, etc., vinylidene halides, such asvinylidene chloride, and the like, acrylic acid; esters of acrylic acid,such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate,cyanoethyl acrylate, and the like; methacrylic acid; esters ofmethacrylic acid such as methyl methacylate, butyl methacrylate, and thelike; vinyl acetate; acrylonitrile; syrene and styrene derivativesincluding alpha-methyl styrene, vinyl toluene, chlorostyrene, vinylnaphthalene; and other monomers having at least one terminal CH₂═C<grouping; mixtures of any one of these types of monomers and other typesof ethylenically unsaturated monomers known to those skilled in the art.

[0027] The peroxydicarbonates of the present invention are particularlyuseful in the suspension polymerization of vinyl chloride to makepolyvinyl chloride (PVC). The invention is further described in theaqueous suspension polymerization of vinyl chloride.

[0028] In the aqueous suspension process to produce PVC from vinylchloride monomer, the polymerization process is usually conducted at atemperature in the range of about 0° C. to 100° C. However, it ispreferred to employ temperatures in the range of about 40° C. to about70° C., since at these temperatures polymers having the most beneficialproperties are produced. The time of the polymerization reaction willvary from about 2 to about 15 hours, preferably from 3 to 6 hours. Theaqueous suspension process to produce PVC contains, in addition to thevinyl chloride monomer, water, dispersants, free radical initiator andmay optionally contain other ingredients such as buffers, short stopagents, and the like. The aqueous suspension process to produce PVC is abatch process for the reaction and then becomes a continuous processafter leaving the reactor. The continuous part of the process involvesstripping the residual vinyl chloride monomer from the PVC polymer andrecovering the monomer for further use in subsequent polymerizations.Also, the polymer particles are dewatered and dried to a free flowingpowder, all as is well understood in the art.

[0029] Once the PVC polymerization reaction reaches the desiredconversion, which is usually from about 80 to 94 percent conversion ofthe monomer to polymer, the reaction is stopped and the reactor contentsare pumped out to empty the reactor. He empty reactor is then preparedfor the next polymerization cycle by flushing with water and coating thewalls to prevent build-up of polymer. The flushing and coating cycleconsumes about 10 to 20 minutes, which is ample time to conduct thereaction to make the peroxydicarbonate which will be used in the nextpolymerization cycle.

[0030] The peroxydicarbonate made by this invention, together with theby-products of the peroxydicarbonate reaction are charged to the PVCreactor at the desired time to begin the polymerization of the vinylchloride monomer. The order of charging the ingredients to the PVCreactor is not critical, however it is preferred to charge theperoxydicarbonate after the reactor contents have reached the desiredpolymerization temperature. If the peroxydicarbonate is added before thedesired polymerization temperature is reached, some of it will be usedup at the lower temperature and result in less initiator being presentfor the polymerization. This can be compensated for by adding an excessof peroxydicarbonate, but is less desirable because of increased costs.

[0031] The yields of the peroxydicarbonate preparation method of thisinvention are from about 90 to about 97% yield. A convenient method todetermine the yield is to measure the PVC reaction cycle time with agiven loading of peroxydicarbonate and compare the reaction time to thetheoretical time, as is well understood in the art. The PVC reactioncycle times indicate that the yields of the peroxydicarbonate made bythe method of this invention is very reproducible and is at least 90%. Aconvenient method is to the charge to the PVC reactor about 10% excessover the theoretical amount required of the peroxydicarbonate producedby this invention. This is to compensate for the less than 100% yield.

[0032] The level and selection of a particular type of peroxydicarbonateused in a PVC polymerization reaction will vary depending on thereaction temperature desired and the total reaction cycle time desired.The total cycle time desired is usually determined by the speed at whichheat can be removed from the PVC reaction. The speed of heat removaldepends on several factors such as the surface area of the reactoravailable for cooling, the cooling medium temperature, and thecoefficient of heat transfer. PVC reactors can be equipped with refluxcondensers to enhance the speed of cooling and refrigerated water can beused on the reactor jacket as well as internal cooling surfaces such asbaffles.

[0033] Normal level of peroxydicarbonate used, when theperoxydicarbonate is di-ethyl peroxydicarbonate is from 0.20 to 1 partby weight per 100 parts by weight of vinyl chloride monomer, preferablyfrom 0.030 to 0.060 part by weight per 100 parts by weight of vinylchloride monomer. Different peroxydicarbonates require different levelsdepending on their decomposition rate to form free radicals at a givenreaction temperature, and their molecular weight, all is well understoodby those skilled in the art. Conventional peroxydicarbonates or otherinitiators can be used in conjunction with the peroxydicarbonates ofthis invention to achieve a particular reaction kinetics, although it isnot necessary, since multiple peroxydicarbonates can be made in the samevessel by the method of this invention.

[0034] One important advantage of this invention is that the entirecontents of the vessel where the peroxydicarbonate is produced can becharged to the PVC polymerization reactor. There is no need to purifythe peroxydicarbonate nor to dilute it with solvents or plasticizers asis taught by the prior art methods.

[0035] The peroxydicarbonates are preferably made on demand, one batchat a time, as needed. This eliminates the need to store theperoxydicarbonate. Of course, the peroxydicarbonates could be made bythe method of this invention and stored for later use, but this is lessdesirable.

[0036] The following examples are presented to show the method of makingperoxydicarbonate and their subsequent use to produce high quality PVCpolymers.

EXAMPLE 1

[0037] In this Example di-ethyl peroxydicarbonate is produced by themethod of this invention. The preparation of the peroxydicarbonate iscarried out in a fume hood. An Arde Barinko homogenizer unit is used. A15 liter beaker is placed within an acetone-dry ice cooling bath held atapproximately −10° C. In addition, an ethylene glycol cooling coil isplaced within the beaker. Temperatures of both the reaction mixture andthe external cooling bath are monitored continuously via glassthermometers clamped in place. The cooling coil operates at from 4° C.to 10° C. 1200 milliliters of water was placed within the 15 liter steelbeaker, followed by 1,000 milliliters of 5 weight percent in water of72.5% hydrolyzed poly vinyl acetate dispersant and 541 milliliters (596grams) of ethyl chloroformate. This mixture was homogenized with an ArdeBarinko homogenizer for approximately one minute, to facilitate theformation of an emulsion of ethyl chloroformate.

[0038] In a separate glass beaker, placed within an ice bath, 4154milliliters (4391 grams) of a 5 weight percent in water of sodiumhydroxide was mixed with 280 milliliters (311 grams) of a 30 weightpercent in water of hydrogen peroxide. Mechanical agitation was used inthe glass beaker. The mixture was stirred mechanically for approximately5 minutes, to facilitate the formation of sodium peroxide (which isformed in equilibrium with sodium hydroxide and hydrogen peroxide) asrepresented by the formula:

2NaOH+H₂O₂

Na₂O₂+2 H₂O

[0039] This mixture containing the sodium peroxide was then placedwithin a glass dropping funnel which was securely clamped above the 15liter stainless steel beaker containing the ethyl chloroformate. Thetemperature within the steel beaker was 0° C. The homogenizer wasrunning throughout the synthesis reaction to form the peroxydicarbonate.

[0040] The sodium peroxide was added dropwise from the glass droppingfunnel, with the addition rate manually adjusted such that thetemperature of the reaction mixture did not rise above 10° C. Thereaction of the sodium peroxide with the ethyl chloroformate can berepresented by the formula:

[0041] At the end of the addition of the sodium peroxide, which was from10-15 minutes, the reaction mixture was homogenized for a further 5minutes while an additional 3500 milliliters of a 5 weight percent inwater of 72.5% hydrolyzed poly vinyl acetate was added to stabilize thedi-ethyl peroxydicarbonate emulsion.

[0042] On a 100% yield basis there would be 489 grams of di-ethylperoxydicarbonate produced.

[0043] The mixture now contains all of the di-ethyl peroxydicarbonateand 72.5% hydrolyzed poly vinyl acetate necessary to provide a dispersedinitiator charge for a 4.2 cubic meter size reactor to polymerize vinylchloride.

[0044] If one wishes to produce different peroxydicarbonates, other thandi-ethyl peroxydicarbonate, to achieve the same activity on an activeoxygen basis, different amounts of the chloroformate would be requiredin the procedure described above according to the following table: TABLE1 Amount chloroformate used Peroxydicarbonate made Chloroformate usedGrams Milliliters Di-ethyl Ethyl chloroformate 596 541 peroxydicarbonaten-propyl n-propyl 673 617 peroxydicarbonate chloroformate Iso-propylIso-propyl 673 624 peroxydicarbonate chloroformate n-butyl n-butylchloroformate 750 698 peroxydicarbonate s-butyl s-butyl chloroformate750 714 peroxydicarbonate 2-ethyl hexyl 2-ethyl hexyl 1058 1080peroxydicarbonate chloroformate

[0045] The amounts of the other ingredients (other than thechloroformate) and the procedure would be the same as described abovefor making di-ethyl chloroformate.

EXAMPLE 2

[0046] This example is presented to show a vinyl chloride suspensionpolymerization using the di-ethyl peroxydicarbonate produced in Example1.

[0047] To a clean 4.2 cubic meter polymerization reactor equipped withagitation and cooling was added 1,479.86 kg of vinyl chloride monomer,2,013.278 kg of hot demineralized water, 3.9173 kg of methyl cellulosedispersant, 2.5243 kg of 88% hydrolyzed poly vinyl acetate dispersantand the aqueous di-ethyl peroxydicarbonate emulsion produced inExample 1. The reaction was started at 56.5° C. and held at thistemperature for 45 minutes. At 45 minutes the reaction temperature wasreduced by 0.038° C. per minute for 185 minutes to a reactiontemperature of 49.5° C. The reaction temperature was held at 49.5° C.until pressure drop occurred. At 312 minutes after the addition of theinitiator pressure drop occurred and 591.9 grams of a short-stop agentwas added to terminate the reaction. The PVC slurry was stripped ofresidual monomer and dried. Examination of the internal metal surfacesof the polymerization vessel showed that the vessel was unexpectedlylacking in polymer build-up, which is very advantageous.

[0048] This example demonstrates that the di-ethyl peroxydicarbonateproduced in Example 1 was very effective in polymerizing vinyl chloridemonomer.

EXAMPLE 3

[0049] This example is presented to show a standard control vinylchloride suspension polymerization using a commercially availablesec-butyl peroxydicarbonate. The same polymerization vessel (4.2 cubicmeters), and reaction ingredients and procedures were followed as inExample 2, except that 669 grams of sec-butyl peroxydicarbonate was usedas the initiator. At 291 minutes after the addition of the initiator,pressure drop occurred and the short-stop agent was added. The PVCslurry was stripped of residual monomer and dried. An examination of theinternal surfaces indicated that there was some polymer build-up, whichis normal for this type of reaction. The polymer build up was greaterfor this reaction than for the reaction of Example 2, which uses theperoxydicarbonate produced by this invention.

EXAMPLE 4

[0050] This example when compared with Example 5 and 6 is presented toshow the superiority of using the di-ethyl peroxydicarbonate produced bythis invention over that used in the prior art method of producing theperoxydicarbonate in the PVC reactor vessel. This example is a controlfor examples 5 and 6.

[0051] A vinyl chloride suspension reaction was conducted in a 55 literpolymerization vessel equipped with agitation and cooling. To a clean 55liter reactor vessel, the following polymerization ingredients wereadded: demineralized water 25.440 Kg Vinyl chloride monomer 18.544 KgPVA (72.5%) 439.898 gr Methyl cellulose 68.681 gr PVA (88%) 35.210 grSec-butyl peroxydicarbonate 8.396 gr

[0052] The water was first added and the agitator started. The VCM wasadded and the reactor contents were heated to 56° C. The dispersantswere then added and agitation continued while maintaining thetemperature at 56° C. for 10 minutes. At this time the commerciallyavailable initiator, secondary-butyl peroxydicarbonate, was added andthe reaction started. The reaction temperature was maintained at 56° C.for 49 minutes. The reaction temperature was gradually reduced as inExample 2 for 197 minutes until it reached 50° C. The temperature wasmaintained at 50° C. until pressure drop occurred. Pressure dropoccurred at 272 minutes after adding the initiator, at which time thereaction was terminated by adding 3.709 gr of a short-stop agent. ThePVC resin slurry was stripped of residual monomer and dried.

EXAMPLE 5

[0053] This example is presented to show that a vinyl chloridesuspension reaction using the di-ethyl peroxydicarbonate produced by themethod of this invention is superior to the method used in the prior artof producing the di-ethyl peroxydicarbonate in the polymerization vessel(as is shown in Example 6).

[0054] The same 55 liter reactor vessel was used in this example as inExample 4 and the same procedures followed as well as the same reactioningredients, except that the 8.396 grams of commercially availablesecondary butyl peroxydicarbonate was replaced with a di-ethylperoxydicarbonate produced as in Example 1 using 8.56 grams of ethylchloroformate. Pressure drop occurred at 274 minutes after addition ofthe initiator and the reaction was terminated at this time by adding ashort stop agent as in Example 4. The PVC resin slurry was stripped ofresidual monomer and dried.

EXAMPLE 6

[0055] This example is presented to show the suspension polymerizationof vinyl chloride monomer using the prior art method of making di-ethylperoxydicarbonate in the polymerization vessel, prior to thepolymerization.

[0056] The same 55 liter reactor was used in this example as in Examples4 and 5 and the same procedures followed as well as the same reactioningredients, except that in this example the di-ethyl peroxydicarbonatewas produced in the reaction vessel and about a 35% excess of initiatoringredients were used to obtain an equivalent time to pressure drop,because of the inefficiency in making the peroxydicarbonate in thereactor vessel.

[0057] To make the initiator in the reactor, 8.1 Kg of water was firstcharged to the reactor (which is about 32% of the total water used) andthe agitator started. It was necessary to have the water level higherthan the agitator level in the reactor in order to get agitation formaking the initiator. The dispersants (72.5% PVA, 88% PVC and methylcellulose) were then charged to the reactor and followed by 10.50 gramsof ethyl chloroformate, 15.4276 grams of sodium hydroxide, and 5.5628grams of hydrogen peroxide. The ingredients were mixed for 5 minutesbefore charging the remaining water. The vinyl chloride monomer was thencharged and temperature brought to 56° C. The temperature profile wasthen the same as in Examples 4 and 5. Pressure drop occurred at 277minutes and the reaction was stopped as in Examples 4 and 5. Theresulting PVC resin slurry was dewatered and dried.

[0058] The PVC resins produced in Examples 4, 5 and 6 were tested forproperties important to PVC resins and the results are shown in TableIII below: TABLE III Example 5 (this Example 6 Resin Property Example 4(control) invention) (comparative) Avg particle size 126 131 146(microns) Particle size 23 23 27 distribution % coarse 0.10 0 0.10 %fines 21.48 19.40 12.61 DOP porosity 0.414 0.394 0.361 (ml/gr.) Apparentbulk 0.419 0.424 0.452 density (gr/ml.) Funnel flow 28.4 27.0 22(seconds) Yellowness Index 8.07 11.63 14.54 DTS - yellow 14 18 10 (min)DTS-black (min) 24 29 22

[0059] From the above data it can be seen that the thermal stability andinitial color (yellowness index) of the PVC resin made with theinitiator produced in the reaction vessel (Example 6) is inferior to thePVC resin produced according to this invention (Example 5). The resinproduced by this invention compares much more favorably to the control(Example 4) which uses a conventional commercially available sec-butylperoxydicarbonate initiator. The yellowness index and the stability(DTS) problems of the prior art method are believed to be caused by thelow yield of peroxydicarbonates made in the reactor thus resulting insignificant amounts of chloroformate not being converted toperoxydicarbonate due to hydrolysis to ethyl carbonic acid and theresulting detrimental effects on the PVC resin by having thesecontaminants present in the polymerization.

[0060] The above examples and description of the invention is notlimited by the specific materials mentioned or examples performed. Theinvention is intended to be limited only by the claims which follow.

1-35. (Canceled)
 36. A free radial initiator for use in thepolymerization of ethylenically unsaturated monomers comprising anaqueous emulsion of at least one organic peroxide wherein the emulsionis comprised of droplets of at least one organic peroxide with diametersof less than 10 μm.
 37. The free radical initiator of claim 36 whereinthe at least one organic peroxide is a peroxydicarbonate.
 38. The freeradical initiator of claim 37 wherein the peroxydicarbonate is selectedfrom the group consisting of di-ethyl peroxydicarbonate, n-propylperoxydicarbonate, iso-propyl peroxydicarbonate, n-butylperoxydicarbonate, s-butyl peroxydicarbonate, and 2-ethyl hexylperoxydicarbonate.
 39. The free radical initiator of claim 36 whereinthe aqueous emulsion comprises at least two organic peroxides.
 40. Thefree radical initiator of claim 38 wherein the emulsion is comprised ofdroplets of the peroxydicarbonate with diameters ranging from about 1 μmto about 4 μm.
 41. A process for producing a free radical initiator foruse in the polymerization of ethylenically unsaturated monomerscomprising the step of forming an aqueous emulsion of at least oneorganic peroxide wherein the emulsion is comprised of droplets of atleast one organic peroxide with diameters of less than 10 μm.
 42. Theprocess of claim 41 wherein the aqueous emulsion of the at least oneorganic peroxide is formed at a temperature of from about 0° C. to about40° C.
 43. The process of claim 42 wherein the aqueous emulsion of theat least one organic peroxide is formed in an in-line homogenizer. 44.The process of claim 42 wherein the aqueous emulsion of the at least oneorganic peroxide is formed by a process comprising the step of forming amixture of at least one peroxide and an aqueous emulsion of at least oneorganic halide wherein the emulsion is comprised of droplets of theorganic halide with diameters of less than 10 μm and wherein the mixturereacts to form an aqueous emulsion of the at least one organic peroxide.45. The process of claim 44 wherein the aqueous emulsion of the at leastone organic peroxide is comprised of droplets of the at least oneorganic peroxide with diameters ranging from about 1 μm to about 4 μm.46. The process of claim 45 wherein the at least one peroxide and theaqueous emulsion of at least one organic halide are combined in anin-line homogenizer.
 47. The process of claim 46 wherein the process iscontinuous.
 48. The process of claim 47 wherein the at least oneperoxide is an alkali metal peroxide.
 49. The process of claim 48wherein the at least one organic halide is a haloformate.
 50. Theprocess of claim 49 wherein the molar ratio of alkali metal peroxide tohaloformate is 2:1.
 51. The process of claim 47 wherein the aqueousemulsion of the at least one organic peroxide comprises at least twoorganic peroxides.
 52. A process for the polymerization of at least oneethylenically unsaturated monomer comprising: (a) adding to apolymerization reactor at least one ethylenically unsaturated monomer;(b) adding to the polymerization reactor a free radical initiatorcomprising an aqueous emulsion of at least one organic peroxide whereinthe emulsion is comprised of droplets of at least one organic peroxidewith diameters of less than 10 μm; (c) conducting the polymerizationreaction to the desired level of conversion of said ethylenicallyunsaturated monomer to form polymer; (d) discharging said polymer fromthe polymerization reactor; and (e) stripping said ethylenicallyunsaturated monomer from said polymer.
 53. The process of claim 52wherein said ethylenically unsaturated monomer is vinyl chloridemonomer.
 54. The process of claim 53 wherein the emulsion is comprisedof droplets of at least one organic peroxide with diameters ranging fromabout 1 μm to about 4 μm.
 55. The process of claim 54 wherein theemulsion comprises at least two organic peroxides.
 56. The process ofclaim 55 wherein the at least one organic peroxide is aperoxydicarbonate.
 57. The process of claim 56 wherein theperoxydicarbonate is selected from the group consisting of di-ethylperoxydicarbonate, n-propyl peroxydicarbonate, iso-propylperoxydicarbonate, n-butyl peroxydicarbonate, s-butyl peroxydicarbonate,and 2-ethyl hexyl peroxydicarbonate.